The embryonic stage extends from 16 days through the end of week 8.

A. Small intestine is the primary site of nutrient absorption. The majority of digestion and absorption of nutrients such as carbohydrates, proteins, and fats occurs in the small intestine, particularly in the duodenum and jejunum.

B. Pancreas secretes digestive enzymes into the small intestine but does not absorb nutrients itself.

C. Stomach plays a role in the digestion of proteins and the mechanical breakdown of food, but it absorbs very few nutrients, primarily alcohol and some drugs.

D. Large intestine absorbs water and electrolytes, but it is not the major site of nutrient absorption. Most nutrients are absorbed before food reaches the large intestine.

A. The endometrium is the inner lining of the uterus that supports the embryo after implantation, but it does not provide direct fetal nutrition or secrete hormones for fetal development.

B. The placenta is the organ that provides fetal nutrition, gas exchange, and waste removal. It also secretes hormones such as human chorionic gonadotropin (hCG), progesterone, and estrogen, which are essential for maintaining pregnancy and supporting fetal development.

C. The blastocyst is the early stage of the embryo that implants into the endometrium, but it does not provide fetal nutrition or secrete pregnancy-regulating hormones.

D. The myometrium is the muscular layer of the uterus responsible for contractions during labor, but it does not provide fetal nutrition or secrete hormones.